Staphylococcus aureus lipoteichoic acid induces the secretion of MUC5AC by activating NADPH oxidase/ROS/TACE/TGF-α/EGFR pathway in human nasal epithelial cells

Aims: The present study is to investigate the effect of Lipoteichoic Acid (LTA) on the secretion of MUC5AC by nasal mucosa cells, as well as the underlying mechanism. Methods: Human nasal epithelial cell line HNEpC was incubated with 10, 20 or 30 mu g/ml LTA for 0-24 h. Enzyme-linked immunosorbent assay was used to determine the concentrations of secreted MUC5AC and Transforming Growth Factor (TGF)-alpha. Quantitative real-time polymerase chain reaction was performed to determine the expression of MUC5AC mRNA. Fluorescence resonance energy transfer analysis was carried out to detect the production of Reactive Oxygen Species (ROS) and the enzymatic activity of tumor necrosis factor-alpha converting enzyme (TACE). Western blotting was used to identify the cell membrane localization of p47phox and p67phox subunits of Duox1 and the phosphorylation of Epidermal Growth Factor Receptor (EGFR). The effect of Duox1/ROS/TACE/TGF-alpha/EGFR signaling pathway on MUC5AC secretion was examined by treating the cells with siRNA of Duox1, ROS inhibitor N-acetyl-cysteine, siRNA of TACE, TGF-alpha neutralizing antibody, or EGFR inhibitor AG-1478. Results: LTA increased the expression and secretion of MUC5AC in dose- and time-dependent manners, possibly via Duox1 and ROS. In addition, LTA promoted the enzymatic activity of TACE via ROS. Moreover, LTA induced the secretion of MUC5AC by promoting the secretion of TGF-alpha via TACE and by the activation of EGFR that was dependent on binding with TGF-alpha. Conclusion: The present study demonstrates that LTA induces the expression and secretion of MUC5AC via Duox1/ROS/TACE/TGF-alpha/EGFR signaling pathway in HNEpC cells.